1. Field of the Invention
The field of the invention is devices for blocking out and locking out operation of circuit breakers and other switches.
2. Background Art
In my prior patent, U.S. Pat. No. 5,122,624, issued Jun. 16, 1992, there is a general description of circuit breakers and devices for preventing their operation. Such devices are more generally identified as block-outs, when they block operation of the switch. When such devices are further secured by a padlock, they are also referred to as lock-outs. Such lock-outs may be included under the broad definition of block-out devices.
Costanza, et al., U.S. Pat. No. 5,079,390, shows a lock-out device for attachment to a solid switch stem, sometimes referred to as a "no-hole" circuit breaker switch stem. This lock-out device has a rigid block with a passage therethrough in which a set screw is inserted to grip a switch stem. A second passage intersects this screw passage behind the screw, so as to permit insertion of a lock shackle to lock out access to the screw.
Jordan, Sr., U.S. Pat. No. 5,147,991, shows another such device including a block, a screw threaded through a portion of the block to grip a switch stem and a slideable cover which is moved into position to block access to the screw and to align a pair of apertures in the body and the cover. A lock shackle fits through these aligned apertures to lock the cover in place and prevent access to the screw.
Such prior devices have a disadvantage of contacting the switch stem directly with the screw. It would be advantageous to distribute the forces applied to the switch stem.
Such devices also require the use of tools for moving the screw, rather than being operable by hand and without the use of such tools.
Such prior devices place the lock in a location which can provide a considerable rotational torque on the switch stem.
There is a need in the art for an improved no-hole lock-out device which is easy to install, low in manufacturing cost, and compact in size.
There is also a need for a device which improves the method of attachment to the switch stem and location of the lock relative to the switch stem.